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FORT BRAGG, N.C. — A top Army general said Wednesday that there was no outside influence in his decision to court-martial Sgt. Bowe Bergdahl over leaving his post in Afghanistan.

Bergdahl, 30, of Hailey, Idaho, walked off his post in Afghanistan in 2009 and wound up as a captive of the Taliban and its allies until 2014. The Obama administration won his release by swapping him for Guantanamo Bay detainees.

Gen. Robert B. Abrams, head of Army Forces Command at Fort Bragg, decided to send the case to a general court-martial rather than a lower-level tribunal. Bergdahl faces charges of desertion and misbehavior before the enemy, and the latter charge carries up to a life sentence.

Bergdahl's defense has alleged that Abrams destroyed evidence by burning about 100 letters he received from the public about the case.

In a rare appearance by a four-star general at a court-martial hearing, Abrams testified that he only "glanced" at the letters to determine their nature before putting them in a burn bag to be destroyed, which he said is common procedure for his correspondence.

"I could tell in the first couple of sentences how this was going to go. Once I recognized the tenor and tone of the letter, I ripped it in half and threw it away," he testified.

Abrams said his legal counsel told him he was not required to keep the letters, and he said in no way did he consider their contents in making his decision.

Bergdahl's lawyers want Abrams disqualified and have another commander decide whether the case warrants a general court-martial.

"I must remain fair and impartial," Abrams said. "I can tune out all of that outside noise. I take that duty very, very seriously."

"Well, that's all well and good for him to say," Eugene Fidell, one of Bergdahl's civilian lawyers, said later. "But we as lawyers representing Sgt. Bergdahl have to be able to evaluate that, and the only way to evaluate the underlying reality is seeing the letters, except we've been disabled from seeing the letters because of his unilateral action."

Prosecutors argue that the letters didn't constitute evidence and that Abrams shouldn't be disqualified.

In addition to the burned letters, the defense cites as reasons to disqualify Abrams his prior role advising former U.S. Defense Secretary Chuck Hagel during efforts to return Bergdahl from captivity and questions about whether Abrams considered defense objections to the findings of a preliminary hearing.

Abrams said he had knowledge of the Bergdahl case while advising Hagel but said he wasn't involved in any of the decision-making.

The military judge overseeing Bergdahl's case, Army Col. Jeffery Nance, said he would rule on the defense motion as soon as possible.

Nance also hasn't yet ruled on a defense motion to dismiss the case over comments by U.S. Sen. John McCain, which they contend amount to undue outside influence. McCain said he would call for a congressional hearing if Bergdahl isn't punished for desertion.

Abrams called the comments "inappropriate" and said "absolutely not" when asked if they swayed his decision.

The trial is scheduled for February 2017, but it might be pushed back because of the volume of classified material that still has to be reviewed by both sides.

Nance granted a motion Wednesday to extend the deadline for the military to turn over classified documents in the case. It's the third time he's granted an extension, and he expressed some impatience over the repeated delays.

Bergdahl, who has said he walked away from his post to draw attention to problems in his unit, has been on desk duty at Fort Sam Houston in Texas since his return to the U.S.